KR102563808B1 - Jelly-Roll Type Electrode Having Anode which anode mixtures comprising active material composition different each other are formed on both sides of electrode current collector, Secondary Battery comprising the same, and Device comprising secondary battery - Google Patents

Abstract

In a jelly-roll type electrode assembly in which a long sheet-structured separator is wound between a sheet-type positive electrode and a negative electrode,
In the negative electrode, a negative electrode mixture is formed on both sides of the negative electrode current collector, and in the negative electrode current collector, when winding to form an electrode assembly, the inner side is the first side and the outer side is the second side. When you say
The first negative electrode mixture coated on the first surface contains 70% by weight or more of artificial graphite as an active material based on the total weight of the active material,
The second negative electrode mixture coated on the second surface is an active material, a jelly-roll type electrode assembly in which natural graphite is included at 70% by weight or more based on the total weight of the active material, a secondary battery including the same, and a device including the secondary battery to provide.

Description

A jelly-roll type electrode assembly including a negative electrode in which negative electrode mixtures including active materials of different compositions are formed on both sides of a current collector, a secondary battery including the same, and a device including the secondary battery {Jelly-Roll Type Electrode Having Anode which anode mixtures comprising active material composition different each other are formed on both sides of electrode current collector, Secondary Battery comprising the same, and Device comprising secondary battery}

The present invention relates to a jelly-roll type electrode assembly including a negative electrode in which negative electrode mixtures including active materials of different compositions are formed on both sides of a current collector, a secondary battery including the same, and a device including the secondary battery.

Recently, as technology development and demand for mobile devices increase, the demand for secondary batteries capable of charging and discharging as an energy source is rapidly increasing, and accordingly, a lot of research on secondary batteries that can meet various needs is being conducted. In addition, secondary batteries are electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles that are proposed as a solution to air pollution caused by conventional gasoline vehicles and diesel vehicles using fossil fuels. (Plug-in HEV) and the like are attracting attention as a power source.

Accordingly, electric vehicles (EVs) that can operate only with secondary batteries, hybrid electric vehicles (HEVs) that use a secondary battery and an existing engine together have been developed, and some of them have been commercialized. As a secondary battery as a power source for EVs and HEVs, nickel metal hydride metal (Ni-MH) secondary batteries are mainly used, but recently, studies using lithium secondary batteries with high energy density, high discharge voltage and output stability have been actively conducted. and some have been commercialized.

Depending on the shape of the battery case, the lithium secondary battery is divided into a cylindrical battery and a prismatic battery in which the electrode assembly is embedded in a cylindrical or prismatic metal can, and a pouch-type battery in which the electrode assembly is embedded in a pouch-type case of an aluminum laminate sheet. are classified

In addition, the electrode assembly built into the battery case is a power generating device capable of charging and discharging, consisting of a cathode, a cathode, and a structure in which a separator is interposed between the anode and the cathode, and a separator is formed between the anode and the cathode in the form of a long sheet coated with an active material. A jelly-roll type wound with a separator interposed, a stacked type in which a plurality of positive and negative electrodes of a predetermined size are sequentially stacked with a separator interposed therebetween, and a full cell composed of electrodes of different polarities on both sides (e.g., anode-separator- A stack-folding type in which a unit cell such as a cathode) or a bicell composed of electrodes of different polarity on both sides (e.g., anode-separator-cathode-separator-anode) is placed on a long sheet-type separator and then wound. are classified

Among them, the jelly-roll type electrode assembly (hereinafter referred to as 'jelly-roll') is easy to manufacture and has high energy per weight, thereby expanding the market for EVs and HEVs using the jelly-roll as a power source. At the same time, the demand for cylindrical secondary batteries is rapidly increasing.

On the other hand, the positive electrode and the negative electrode are generally manufactured by applying an electrode mixture containing an active material on both sides of each current collector, and the winding side is the top side and the opposite side is the back side. At this time, the top surface and the back surface inevitably have different stresses generated by winding.

However, in the prior art, the same active material composition was coated on the top and back surfaces according to the loading. Specifically, in the case of a negative electrode using a mixture of artificial graphite and natural graphite as an anode active material, the coating layer is detached from the side end in the longitudinal direction on the back surface. There was a problem that occurred.

In addition, the negative electrode mixture desorbed in this way acts as an impurity inside the secondary battery, causing a problem of deteriorating the performance of the secondary battery.

Therefore, there is a high need for a jelly-roll type electrode assembly having improved output, capacity and lifespan characteristics by solving the above problems.

An object of the present invention is to solve the problems of the prior art and the technical problems that have been requested from the past.

Specifically, an object of the present invention is to prevent detachment of the negative electrode mixture due to winding by forming the negative electrode of the jelly-roll type electrode assembly in which a negative electrode mixture containing active materials of different compositions is coated on both sides of a negative electrode current collector. To provide an electrode assembly capable of improving the output, capacity, and lifespan characteristics of a secondary battery including the same.

Another object of the present invention is to further maximize the effect by solving problems such as lithium precipitation by adjusting the N / P ratio of the negative electrode and the positive electrode.

According to the present invention for achieving this object,

In a jelly-roll type electrode assembly in which a long sheet-structured separator is wound between a sheet-type positive electrode and a negative electrode,

In the negative electrode, a negative electrode mixture is formed on both sides of the negative electrode current collector, and in the negative electrode current collector, when winding to form an electrode assembly, the inner side is the first side and the outer side is the second side. When you say

The active material of the first negative electrode mixture coated on the first surface contains more artificial graphite than natural graphite,

A jelly-roll type electrode assembly in which natural graphite is included more than artificial graphite in the active material of the second negative electrode mixture coated on the second surface is provided.

That is, unlike the prior art, the jelly-roll type electrode assembly according to the present invention is coated with a negative electrode mixture including negative electrode active materials of different compositions on the first and second surfaces of the negative electrode current collector, so that the second It is possible to improve the output, capacity, and lifespan characteristics of a secondary battery including the negative electrode mixture by preventing detachment of the negative electrode mixture on both sides by increasing the adhesiveness of the negative electrode mixture on the surface to the current collector.

In addition, the first negative electrode mixture and the second negative electrode mixture may include, for example, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, carbon nanotube, fullerene, activated carbon, etc., in addition to the natural graphite and artificial graphite. carbon and graphite materials other than graphite and artificial graphite; Metals such as Al, Si, Sn, Ag, Bi, Mg, Zn, In, Ge, Pb, Pd, Pt, Ti, etc., which can be alloyed with lithium, and compounds containing these elements; composites of metals and their compounds with carbon and graphite materials; A lithium-containing nitride or the like may be further included.

In this case, in detail, in the active material of the first negative electrode mixture, artificial graphite and natural graphite are included in an amount of 61 to 99% by weight: 1 to 39% by weight, based on the weight, and the active material of the second negative electrode mixture includes artificial graphite and Natural graphite may be included in 1 to 39% by weight: 61 to 99% by weight based on weight.

More specifically, in the active material of the first negative electrode mixture, artificial graphite and natural graphite may be included in an amount of 70 to 99% by weight: 1 to 30% by weight, respectively, based on the weight, and the active material of the second negative electrode mixture includes artificial graphite and Natural graphite may be included in an amount of 1 to 30% by weight: 70 to 99% by weight, respectively, and most specifically, the first negative electrode mixture contains 75 to 85% by weight of artificial graphite and natural graphite in the active material. Weight%: 15 to 25% by weight, and in the active material of the second negative electrode mixture, artificial graphite and natural graphite may be included at 15 to 25% by weight: 75 to 85% by weight.

More specifically, the active material included in the first negative electrode mixture and the second negative electrode mixture may be composed of natural graphite and artificial graphite having the above composition.

This is because artificial graphite has excellent output characteristics and lifespan characteristics, while natural graphite has excellent adhesive strength. More specifically, since less stress is applied to the first negative electrode mixture formed on the first surface that is wound inward, there is less problem of detachment, so that a large amount of artificial graphite having excellent output, capacity, and lifespan characteristics is contained, Since the second negative electrode mixture formed on the second surface that is wound outward has a stronger stress, it is possible to solve the conventional problem by including a large amount of natural graphite having strong adhesive strength in consideration of easy detachment. .

Here, the natural graphite exhibiting excellent adhesion can sufficiently secure the mechanically interlocking effect of adhesion between particles through the binder as the specific surface area increases, so that 2 m ² /g to 8 m ² /g , and specifically, it may be 2.1 m ² /g to 4 m ² /g. On the other hand, artificial graphite may have a specific surface area (BET) of 0.5 m ² /g to 5 m ² /g, and specifically, 0.6 m ² /g to 4 m ² /g.

The specific surface area can be measured by the Brunauer-Emmett-Teller (BET) method. For example, it can be measured by the BET 6-point method by the nitrogen gas adsorption distribution method using a porosimetry analyzer (Bell Japan Inc, Belsorp-II mini).

The shape of the natural graphite is not limited, and may be flake graphite, vein graphite, or amorphous graphite, in detail, flake graphite or amorphous graphite, more specifically, Since the contact area between particles increases, the adhesion area increases and thus the adhesion is improved, it is preferable to have a high tap density or bulk density, and it is preferable that the crystal grain orientation of natural graphite exhibits anisotropy, so it may be earthy graphite.

On the other hand, the shape of the artificial graphite is not limited, and may be powder, flake, block, plate, or rod, but in detail, in order to exhibit the best output characteristics, the shorter the moving distance of lithium ions, the better. , In order for the movement distance in the direction of the electrode to be short, it is preferable that the crystal grain orientation of the artificial graphite exhibit isotropy, so it may be in the form of flakes or plates in detail, and more specifically in the form of flakes.

The natural graphite may have a tap density of 0.9 g/cc to 1.3 g/cc, specifically 0.92 g/cc to 1.15 g/cc, and the artificial graphite may have a tap density of 0.7 g/cc to 1.1 g/cc. It may be cc, and specifically may be 0.8 g/cc to 1.05 g/cc.

Here, the tap density is obtained by putting 50 g of the precursor in a 100 cc tapping cylinder and then tapping 3000 times using a JV-1000 measuring device manufactured by COPLEY.

Outside the above range, if the tap density is too small, the contact area between the particles is not sufficient, resulting in deterioration in adhesive strength. There is a problem that the output characteristics of the deterioration, which is not preferable.

Meanwhile, the first negative electrode mixture and the second negative electrode mixture may further include a conductive material and a binder.

The conductive material is not particularly limited as long as it is a conventionally known conductive material and has conductivity without causing chemical change in the battery. For example, carbon black, acetylene black, Ketjen black, channel black, furnace black, carbon black such as lamp black and summer black; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives may be used.

The binder is not limited as long as it is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, and examples thereof include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, Hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluoro rubber , various copolymers, etc., respectively.

At this time, the conductive material and the binder are each 0.1 to 30% by weight, specifically, 0.5 to 5% by weight, more specifically, 1 to 3% by weight based on the total weight of the first negative electrode mixture or the second negative electrode mixture. may be included in weight percent.

At this time, within the above content range, the binder may be included in the same content in the first negative electrode mixture and the second negative electrode mixture, but in a different content, specifically, with a higher content in the second negative electrode mixture formed on the second surface that is wound outward. may also be included.

Furthermore, a filler or the like may be selectively further included in each of the first negative electrode mixture and the second negative electrode mixture.

The filler is selectively used as a component that suppresses expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery, and examples thereof include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The anode current collector is generally manufactured to a thickness of 3 to 200 μm, and is not particularly limited as long as it has conductivity without causing chemical change to the battery. For example, copper, stainless steel, aluminum, nickel , titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, fine irregularities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics.

In addition, at least one of the first and second surfaces of the negative electrode may have a non-coated portion on which the negative electrode current collector is not coated, and a negative electrode tab may be attached to the non-coated portion.

The negative electrode tab may be attached by ultrasonic welding, but is not limited to the above method, and various tab attachment techniques may be applied.

The uncoated portion may be formed at a winding start point or a middle portion in the longitudinal direction among both ends in the longitudinal direction of the sheet-shaped negative electrode, and the location thereof is not limited and may be variously selected.

Meanwhile, the positive electrode may have a structure in which a positive electrode mixture including a positive electrode active material, a conductive material, and a binder is formed on both sides of a positive electrode current collector.

Like the negative electrode, the positive electrode mixture including positive electrode active materials having different compositions may be formed on both sides of the positive electrode current collector. At this time, an active material having better adhesive strength may be included on the surface that is wound outward like the negative electrode. Of course, a positive electrode mixture including a positive electrode active material having the same composition may be formed.

The cathode current collector is generally manufactured to a thickness of 3 to 200 μm, and is not particularly limited as long as it does not cause chemical change in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, Titanium, and one selected from aluminum or stainless steel surface-treated with carbon, nickel, titanium, or silver may be used, and in detail, aluminum may be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may have various forms such as film, sheet, foil, net, porous material, foam, and non-woven fabric.

The cathode active material may include, for example, layered compounds such as lithium cobalt oxide (LiCoO ₂ ) and lithium nickel oxide (LiNiO ₂ ), or compounds substituted with one or more transition metals; Formula Li _{1 + x} Mn _{2 - x} O ₄ (Here, x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ and the like lithium manganese oxide; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _{1 - x} M _x O ₂ (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3); Formula LiMn _{2 - x} M _x O ₂ where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1 or Li ₂ Mn ₃ MO ₈ where M = Fe, Co, Ni, Cu or Zn) lithium manganese composite oxide; LiMn ₂ O ₄ in which Li part of the formula is substituted with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ etc. are mentioned, but it is not limited only to these.

The specific types of the conductive material and binder are as described in the negative electrode, and the content thereof is 0.1 to 30% by weight, specifically, 0.5 to 5% by weight, based on the total weight of the positive electrode mixture in each positive electrode mixture. More specifically, it may be included in 1 to 3% by weight.

Meanwhile, the same amount of the binder may be included in the positive electrode mixture formed on both sides of the positive electrode current collector, and may be included in a larger amount in the positive electrode mixture formed on the outer side of the current collector.

In addition, as described in the case of the negative electrode, the positive electrode mixture may further include a filler.

In addition, a non-coated portion to which the cathode mixture is not applied may be formed on one or both surfaces of the cathode current collector, and a cathode tab may be attached to the non-coated portion.

The positive electrode tab may be attached by ultrasonic welding, but is not limited to the above method, and various tab attachment techniques may be applied.

The uncoated portion may be formed at a winding start point or a middle portion in the longitudinal direction among both ends in the longitudinal direction of the sheet-shaped anode, and the location thereof is not limited and may be variously selected.

The separator having a long sheet structure interposed between the anode and the cathode is an insulating thin film having high ion permeability and mechanical strength. The pore diameter of the separator is generally 0.01 to 10 μm, and the thickness is generally 5 to 300 μm. Examples of such a separator include olefin-based polymers such as chemical-resistant and hydrophobic polypropylene; A sheet or non-woven fabric made of glass fiber or polyethylene is used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may serve as a separator.

On the other hand, the N / P ratio of the electrode assembly manufactured as described above may be 1 or more (N / P ratio ≥ 1), and in detail, the N / P ratio is 1 or more to 1.5 or less (1≤N / P ratio≤ 1.5).

The N / P raito is a capacity ratio per unit area of the cathode and anode, and can be calculated as (capacity per unit area of the cathode) / (capacity per unit area of the cathode) x 100.

The capacity per unit area of the electrode means a value obtained by dividing the theoretical discharge capacity (mAh) for each electrode in the battery by the electrode area (cm ² ).

According to the present invention, by controlling the N / P ratio within the above range, it is possible to prevent deterioration of life characteristics due to lithium deposition on the negative electrode and to increase the stability of the secondary battery.

When the capacity ratio per unit area of the negative electrode and the positive electrode is out of the above range and the N/P ratio is 1 or less, lifetime deterioration occurs due to lithium precipitation, and safety is seriously threatened.

The N / P ratio can be adjusted by adjusting the capacity per unit area of the negative electrode and the capacity per unit area of the positive electrode, and, for example, it can be satisfied by adjusting the area ratio, thickness ratio, and specific surface area of the active material .

Specifically, the positive electrode has a capacity per unit area of the positive electrode mixture formed on one surface of the positive electrode current collector of 4.300 mAh/cm ² to 4.400 mAh/cm ² , and the negative electrode has a unit of negative electrode mixture formed on one surface of the negative electrode current collector. The capacity per area may be 4.500 mAh/cm ² to 4.600 mAh/cm ² .

According to the present invention, also

A secondary battery having a structure in which the jelly-roll type electrode assembly is impregnated with a lithium-containing non-aqueous electrolyte solution and is embedded in a cylindrical or prismatic metal battery case is provided. That is, the secondary battery may be a lithium secondary battery.

The lithium-containing non-aqueous electrolyte is composed of a non-aqueous electrolyte and a lithium salt.

Examples of the nonaqueous electrolyte include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, and gamma-butyl Rolactone, 1,2-dimethoxyethane, tetrahydroxy franc, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxorane, formamide, dimethylformamide, dioxorane, aceto Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxy methane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative , tetrahydrofuran derivatives, ether, aprotic organic solvents such as methyl propionate and ethyl propionate may be used.

The lithium salt is a material that is easily soluble in the non-aqueous electrolyte, and is, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, lithium chloroborane, lithium lower aliphatic carbonate, lithium 4 phenyl borate, imide, etc. can be used. there is.

In some cases, an organic solid electrolyte, an inorganic solid electrolyte, or the like may be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphoric acid ester polymers, poly agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, ions A polymer containing a sexual dissociation group or the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitride, halide, sulfate, and the like of Li such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , etc. may be used.

In addition, for the purpose of improving charge and discharge characteristics, flame retardancy, etc. in the non-aqueous electrolyte solution, for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme (glyme), hexaphosphoric acid triamide , nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxy ethanol, aluminum trichloride, etc. may be added. may be In some cases, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included to impart incombustibility, and carbon dioxide gas may be further included to improve high-temperature storage properties.

Since the structure of the cylindrical or prismatic metal battery case is disclosed in the art, a description thereof is omitted in the present specification.

The lithium secondary battery can be used as a power source for devices, such as mobile phones, portable computers, smart phones, tablet PCs, smart pads, netbooks, light electronic vehicles (LEVs), electric vehicles, hybrid electric vehicles, and plug-in devices. It may be selected from hybrid electric vehicles, power storage devices, and the like.

Since the structure and manufacturing method of such a device are known in the art, a detailed description thereof is omitted in the present specification.

As described above, the jelly-roll type electrode assembly according to the present invention is prepared by forming a negative electrode mixture including negative electrode active materials of different compositions on both sides of a negative electrode current collector, and specifically, the first surface wound inwardly By forming a negative electrode mixture containing a large amount of artificial graphite and a large amount of natural graphite on the outerly wound second surface, respectively, to prevent detachment of the outer negative electrode mixture, thereby improving the output, capacity, and lifespan of a secondary battery including the negative electrode mixture. effect can be exerted.

In addition, by adjusting the N / P ratio of the negative electrode and the positive electrode, life deterioration due to lithium precipitation can be prevented and safety can be secured.

1 is a schematic vertical cross-sectional view of a jelly-roll type electrode assembly according to an embodiment of the present invention before winding;
Figure 2 is a graph showing the results according to Experimental Example 1 of the present invention;
3 is a photograph showing the results according to Experimental Example 3 of the present invention.

Hereinafter, description will be made with reference to drawings according to embodiments of the present invention, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

1 shows a schematic diagram of a jelly-roll type electrode assembly (hereinafter referred to as 'jelly-roll') before winding according to one embodiment of the present invention.

Referring to FIG. 1 , the jelly-roll type electrode assembly 100 according to the present invention has a structure in which a separator 130 is interposed between a sheet-shaped positive electrode 110 and a negative electrode 120 and is wound in the direction of the arrow.

In the positive electrode 110, positive electrode mixtures 112 and 113 are formed on both sides of the positive electrode current collector 111, and in the negative electrode 120, negative electrode mixtures 122 and 123 are formed on both sides of the negative electrode current collector 121. is formed

Here, the negative electrode 120 has a first negative electrode mixture 122 coated on a first surface, which is a surface wound inward with respect to the winding direction, that is, a winding direction, and a second material coated on a second surface, which is a surface wound outward. 2 includes a negative electrode mixture (123).

At this time, the first negative electrode mixture 122 includes artificial graphite as an active material in an amount of 70% by weight or more based on the total weight of the active material, and the second negative electrode mixture 122 contains natural graphite as an active material in an amount of 70% by weight or more based on the total weight of the active material. It is included at 70% by weight or more on a basis.

In addition, the negative electrode 120 has a non-coated portion not coated with the negative electrode mixture on at least one surface of the first or second surface of the negative electrode current collector 121, the negative electrode tab 124 is attached to the uncoated portion, and the positive electrode Similarly to the negative electrode 120, the negative electrode 110 also has a non-coated portion on one surface of the positive electrode current collector 111, to which the positive electrode mixture is not applied, and a positive electrode tab 114 is attached to the uncoated portion.

The jelly-roll type electrode assembly 100 of the structure shown in FIG. 1 is wound in the direction of the arrow, that is, the jelly-roll type electrode assembly of the wound structure is completed.

Hereinafter, the present invention will be further detailed through examples, but the following examples are intended to illustrate the present invention, and the scope of the present invention is not limited to these only.

<Production Example 1>

anode composite manufacturing

LiNi _{1/3 Mn 1/3} Co _1/3 O ₂ was _{used as} a cathode active material _{, and NMP} (N-methyl-2- pyrrolidone) and mixed to prepare a positive electrode mixture.

<Production Example 2>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 30% by weight: 70% by weight was used, and the mixture, conductive material (carbon black), and binder (PVdF) were mixed in a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 3>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 10% by weight: 90% by weight is used, and the mixture, conductive material (carbon black), and binder (PVdF) are mixed at a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 4>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 20% by weight: 80% by weight is used, and the mixture, conductive material (carbon black), and binder (PVdF) are mixed in a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 5>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 90% by weight: 10% by weight is used, and the mixture, conductive material (carbon black), and binder (PVdF) are mixed in a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 6>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 80% by weight: 20% by weight was used, and the mixture, conductive material (carbon black), and binder (PVdF) were mixed at a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 7>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 70% by weight: 30% by weight was used, and the mixture, conductive material (carbon black), and binder (PVdF) were mixed in a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Production Example 8>

cathode composite manufacturing

As an anode active material, a mixture of artificial graphite and natural graphite at 50% by weight: 50% by weight is used, and the mixture, conductive material (carbon black), and binder (PVdF) are mixed in a weight ratio of 98: 1: 1 NMP (N -methyl-2-pyrrolidone) and mixed to prepare a negative electrode mixture.

<Example 1>

Manufacture of anode

The positive electrode mixture prepared in Preparation Example 1 was coated on both sides of a 15 μm-thick aluminum foil at a loading amount of 4.320 mAh/cm ² , and then rolled and dried to prepare a positive electrode.

cathode fabrication

The negative electrode mixture prepared in Preparation Example 3 was coated on one side of a 10 μm-thick copper foil with a loading of 4.566 mAh/cm ² , and the negative electrode mixture prepared in Preparation Example 5 was coated on the other side of the copper foil with a loading of 4.566 mAh/cm ² After coating with a loading amount of, a negative electrode was prepared by rolling and drying.

jelly- roll Manufacture of electrode assembly

A separator having a long sheet structure of polyethylene was interposed between the negative electrode and the positive electrode, and as shown in FIG. 1, the negative electrode mixture prepared in Preparation Example 5 was wound so that the side on which the negative electrode mixture was formed was the inner surface of the winding to prepare a jelly-roll type electrode assembly.

Manufacturing of secondary batteries

The jelly-roll type electrode assembly is housed in a cylindrical battery case, ethyl carbonate, dimethyl carbonate and ethylmethyl carbonate are mixed in a 1: 1: 1 ratio based on the volume ratio, and 1 M LiPF ₆ is included as a lithium salt. A cylindrical secondary battery was prepared by adding a non-aqueous electrolyte.

<Example 2>

The negative electrode mixture prepared in Preparation Example 4 was coated on one side of a 10 μm-thick copper foil with a loading of 4.566 mAh/cm ² , and the negative electrode mixture prepared in Preparation Example 6 was coated on the other side of the copper foil with a loading of 4.566 mAh/cm ² After coating with a loading amount of, a negative electrode was prepared by rolling and drying, and the negative electrode mixture prepared in Preparation Example 6 was wound so that the side on which the negative electrode mixture was formed became the inner surface of the winding to prepare a jelly-roll type electrode assembly. In the subsequent step, a cylindrical secondary battery was manufactured in the same manner as in Example 1.

<Example 3>

The negative electrode mixture prepared in Preparation Example 2 was coated on one side of a 10 μm-thick copper foil with a loading of 4.566 mAh/cm ² , and the negative electrode mixture prepared in Preparation Example 7 was coated on the other side of the copper foil with a loading of 4.566 mAh/cm ² After coating with a loading amount of, a negative electrode was prepared by rolling and drying, and the negative electrode mixture prepared in Preparation Example 7 was wound so that the side on which the negative electrode mixture was formed became the inner surface of the winding to prepare a jelly-roll type electrode assembly. In the subsequent step, a cylindrical secondary battery was manufactured in the same manner as in Example 1.

<Comparative Example 1>

The negative electrode mixture prepared in Preparation Example 8 was coated on both sides of a 10 μm thick copper foil at a loading amount of 4.566 mAh/cm ² , then rolled and dried to prepare a negative electrode, and the negative electrode and the negative electrode prepared in Preparation Example 1 A jelly-roll type electrode assembly was prepared by interposing a separator having a long sheet structure of polyethylene between the positive electrodes and winding the separator. In the subsequent steps, a secondary battery was manufactured in the same manner as in Example 1.

<Experimental Example 1> (Output characteristics)

After the secondary batteries prepared in Examples 1 to 3 and Comparative Example 1 were activated under a current condition of 0.1C in a voltage range of 2.5 V to 4.2 V, each C-rate (charge-rate), D-rate Capacity for each (discharge-rate) was measured, and the results are shown in FIG. 2 below.

Referring to FIG. 2 , it can be seen that the output characteristics of the examples are superior to those of Comparative Example 1.

<Experimental Example 2> (life characteristics)

The secondary batteries prepared in Examples 1 to 3 and Comparative Example 1 were cycled 140 times under the condition of 1.0C in a voltage range of 2.5V to 4.2V to measure energy, and energy retention rate (%) compared to the initial cycle measured, and the results are shown in FIG. 3 below.

Here, energy is the capacity multiplied by the average discharge voltage of the battery.

Referring to FIG. 3, the energy retention rate of Examples 1 to 3 compared to Comparative Example 1 is excellent.

<Experimental Example 3>

In Experimental Example 2, the secondary battery of Example 1 and the secondary battery of Comparative Example 1 after 100 cycles were disassembled to confirm desorption of the negative electrode mixture from the negative electrode, and the resulting photograph is shown in FIG. 4 below.

Referring to Figure 4, in the case of Comparative Example 1, it can be confirmed that the separation of the mixture occurred at both ends in the longitudinal direction from the negative electrode. It was photographed against a black background so that the tally part could be clearly seen.

On the other hand, in the case of Example 1, it can be confirmed that the negative electrode mixture did not desorb from the negative electrode.

Those skilled in the art to which the present invention pertains will be able to make various applications and modifications within the scope of the present invention based on the above information.

Claims (15)

In a jelly-roll type electrode assembly in which a long sheet-structured separator is wound between a sheet-type positive electrode and a negative electrode,
In the negative electrode, a negative electrode mixture is formed on both sides of the negative electrode current collector, and in the negative electrode current collector, when winding to form an electrode assembly, the inner side is the first side and the outer side is the second side. When you say
The active material of the first negative electrode mixture coated on the first surface includes artificial graphite and natural graphite in an amount of 75 to 85% by weight: 15 to 25% by weight,
A jelly-roll type electrode assembly comprising 15 to 25% by weight: 75 to 85% by weight of artificial graphite and natural graphite in the active material of the second negative electrode mixture coated on the second surface. delete delete delete The jelly-roll type electrode assembly of claim 1, wherein active materials included in the first negative electrode mixture and the second negative electrode mixture are composed of natural graphite and artificial graphite. The jelly-roll type electrode assembly of claim 1, wherein the first negative electrode mixture and the second negative electrode mixture include a conductive material and a binder. The jelly-roll type electrode assembly of claim 6, wherein the conductive material and the binder are included in an amount of 1% to 3% by weight based on the total weight of the negative electrode mixture in each negative electrode mixture. The method of claim 1, wherein at least one of the first and second surfaces of the negative electrode has a non-coated portion on which the negative electrode current collector is not coated, and a negative electrode tab is attached to the non-coated portion. electrode assembly. The jelly-roll type electrode assembly according to claim 1, wherein the positive electrode is formed with a positive electrode mixture including a positive electrode active material, a conductive material, and a binder on both sides of a positive electrode current collector, respectively. 10. The jelly-roll type electrode assembly of claim 9, wherein the conductive material and the binder included in the positive electrode mixture are included in an amount of 1% to 3% by weight based on the total weight of the positive electrode mixture in each positive electrode mixture. 10. The jelly-roll type electrode assembly of claim 9, wherein a non-coated portion to which the cathode mixture is not coated is formed on one or both surfaces of the cathode current collector, and a cathode tab is attached to the non-coated portion. The jelly-roll type electrode assembly according to claim 1, wherein an N/P ratio of the electrode assembly is ≥ 1. The method of claim 1, wherein the positive electrode has a capacity per unit area of the positive electrode mixture formed on one surface of the positive electrode current collector of 4.300 mAh/cm ² to 4.400 mAh/cm ² , and the negative electrode is formed on one surface of the negative electrode current collector. A capacity per unit area of 4.500 mAh/cm ² to 4.600 mAh/cm ² Jelly-roll type electrode assembly. A secondary battery having a structure in which the jelly-roll type electrode assembly according to any one of claims 1 and 5 to 13 is impregnated in a lithium-containing non-aqueous electrolyte and embedded in a cylindrical or prismatic metal battery case. The secondary battery according to claim 14, wherein the secondary battery is a lithium secondary battery.

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